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January 3, 2014

Different Colors Attract Sweet Potato Weevils

by editor

Entomological Society of America

The sweet potato weevil, Cylas formicarius (Fabricius), is the most serious pest of sweet potato around the world, damaging sweet potatoes in the field and in storage. Because the larval period is spent within vines or tubers, and the adults are nocturnal, chemical control frequently is not effective.

Mass trapping using synthetic pheromones has suppressed populations of sweet potato weevil males in several countries, but it has not reduced the damage greatly. However, a new study published in Annals of the Entomological Society of America suggests that the color of the traps may affect their usefulness.

For years Dr. Gadi V.P. Reddy (Montana State University) has been searching for the right formula to control this insect without the use of toxic pesticides. In his most recent study with Nirupa Gadi (University of Guam), the researchers found that green traps were most effective in attracting the weevils in indoor conditions, while red traps were most effective in outdoor field conditions.

"Sweetpotato weevils responded to pheromone baited traps of different colors differently in the field and indoors," said Dr. Reddy. "In the field, sweetpotato weevils preferred red, and particularly light red, over the other colors, but indoors, green traps were favored. We have no explanation for the difference. Further studies focusing on why insect behavior changes from outdoors to indoors will be required to find out."